What does "RASN BR" signify in weather conditions?

The abbreviation "RASN BR" is derived from meteorological shorthand, where "RA" stands for rain, "SN" for snow, and "BR" indicates mist or fog. Therefore, this notation conveys that there are moderate levels of both rain and snow occurring, accompanied by mist or fog conditions. The presence of both rain and snow signifies a mix of precipitation type typically seen when temperatures hover around the freezing point, allowing for both forms of moisture to coexist.

In this context, the mention of fog or mist ("BR") adds another layer to the weather conditions, indicating reduced visibility due to the moisture present in the air. This is especially important for transportation and safety issues, making it crucial for observers to accurately note such conditions.

The other options do not fully capture the combination of precipitation and visibility reductions indicated by "RASN BR." Heavy rain and snow or just rain and mist do not accurately reflect the moderate intensity of both rain and snow alongside fog that the abbreviation specifies. Understanding this notation helps observers to communicate weather conditions more effectively and to anticipate the impact on visibility and safety.